Process of making borneol and borneol esters from pinene.



To all whom it may concern:

G-EZA AUSTERWEIL, OF NEUILLY, NEAR PARIS, FRANCE.

PROCESS OF MAKING BORNEOL AND BORNEOL ESTIl-ZIRS FROM PINENE.

No Drawing.

Be it known that I, GiizA AUSTERWEIL, chemist, subject of the King of Hungary, residing at Neuilly, near Paris, 118 Boulevard Bineau, in the Republic of France, have invented certain new and useful Imrovements in an Improved Process for aking Borneol and Borneol Esters from Pinene, of which the following is a full,

clear, and exact description.

The present methods of convertin pinene, by hydration, into alcohols 10' the pentocean series are based on the processes of Bouchardat and Lafont, as described in Oomptes Remius, Volume 113, page 551, and Volume 126, page 755;Ammles dc Chim-z'e at Physique, Series 6, Volume 16, pages 236, 250, and Semmlers treatisepon essential oils, (Die Aethem'sohcn Oele nach z'hren Ghemz'shen Bestcmdteilen) Volume II, page 254.

The processes hitherto proposed are not adapted for technical application: ,(1) because they give poor yields; (2) because resinification, more particularly where acids of the fatty series are employed, occurs to a large extent; (3) because the by-products are diflicult of utilization, and (4) because the resultant alcohols of the pentocean series do not consist of pure borneol and isoborneol, but contain a considerable quantity of admixed fenchyl alcohol, which on oxidation yields fencho derivatives and," in the manufacture of synthetic camphor, may

have a deleterious effect. a

- In carrying out the present rocess, which largely avoids the specified di culties, pinene is heated in an autoclave, with a slight excess of the theoretically-requisite quantity of an aromatic poly-substituted acid insoluble or diflicultly soluble in water. The acids which do not fall under Victor Meyers law of sterical hindrance for esterification are preferably employed. See Bem'chte des Deutschen Ohema'schen GeseZZ- schaft, Vol. 27, 1894, pp. 510 and 1580; Vol. 28,1895, pp. 182, 1254 and 1267. The principle of this law is that if one has to esterify an alcohol with aromatic acids it is better not to use for this purpose diortho-substituted Specification of Letters Patent.

Application filed November 11, 1908. Serial No. 462,024.

I. pinene.

acids, as these will not be esterified as well as the'other acids. By using these acids 21 more favorable yield of borneol rand isoborneol esters is obtained, the formation.

of fenchyl alcohol being almost entirely avoided, probably by reason of sterical impeding. To these acids a certain quantity of their anhydrids is preferably addedfin Patented Mar, '7, 1911.1

order to increase the yield of borneols, these i anhydrids acting on any water still present, retarding formation of the bodies of the hexagonal-ring systems. The use of anhydrids is also desirable, because these, as is well known, hydrate to acids and will therefore attract or absorb the water contained in the t'erpene oil, becoming converted into acids and thus still better dehydrating the The yield is also improved if instead of' the anhy'drid, or even in its presence, the acid chlorid of the respective acid is present in suflicient quantity, whereby also the reaction is accelerated. Probably forthe same reasons as with acid chlorid (formation of 1101), a small addition of pinene 'hydrochlorid acts favorably on the acceleration of the reaction and on the improvement of the yield.-: Ortho-substituted aromatic acids may also'be employed for the reaction, so far as they form an exception to Victor Meyers above mentioned law, 6. 9., nitrophtalic- 1,2, 3, acid, (Bem'okte den Deutschen Ohe-m. Ges. 34486, Monatshefte f.

Chem/66,1900, 27787). The use of an inert gas under pressure, in the autoclave, also ,makes it possible to employ fatty acids and mono-substituted aromatic acids, the latter then giving favorable yields of borneol esters, usually more than 40%.

The quantity of acid necessary for the reaction is dependent on the constitution of the acid used, one molecule of pinene being employed and there being-two molecular proportions of monovalent acid or one molecular proportion of bivalent acid taking part inthe reaction, while the acid may be present in a slight excess. This calculation is in contradiction to the statements of French Patent No. 379,430, as according to Semmlers treatise, Volume II, page 61,

two acid-hydrogen atoms must attach themselves to the pinene. The boiling point of the mixture of acid and pinene, including the anhydrid if used, is first ascertained, and the reaction is caused to take place at a temperature which-lies slightly, say 1020 C., above that which the mixture of liquid had when beginning to boil. If the temperature is thus regulated, the splitting off of water from the isoborneol, with formation of camphene, is almost entirely prevented. After the charging and closing of the autoclave but before the heating, carbon dioxid or any other inert gas is forced in through a nozzle, in order to expel the air and to obtain a pressure exceeding atmospheric pressure. After heating, the mass is discharged from the autoclave, cooled, freed from the surplus acid, which crystallizes out, and the limonene driven oil with steam. The remaining borneol ester and isoborneol est-er are sa onified with the calculated quantity of al ali or alkaline earth and the borneol or isoborneol afterward also driven off with steam, or the saponification-product is directly oxidized to camphor.

It is important to limit the reaction between the acid and pinene to the shortest possible time, because, the process being considered as an esterification of the terpene alcohols, the speed of esterification of the borneol is greater than that of all the other terpene alcohols here occurring (borneol, .011, isoborneol, .0077, terpineol, .00043), and if the reaction lasts longer, more of other alcohols may be formed and thus the yield of the borneol is decreased; also because there is a saving of fuel. The reduction of the time of the reaction is attained by increasing the pressure in the autoclave, whereby also the lessening .in the production of other alcohols, more particularly fenchylalcohol, is effected. The reason is that, under otherwise identical conditions, the specifically heavier isomers are usually formed under pressure. Of the terpene alcohols mentioned, borneol has the greatest specific gravity (borneol 1.02, isofenchyl-alcohol .961, tcrpineol .931). Terpineol is here mentioned because the limonene forms by water splitting from the intermediately-formed terpineol.

The following is a specific example of the process :Equi-molecular weights of pinene and of any poly-substituted organic aromatic acid, 6. 9., nitrophtalic acid 1, 2, 3, are mixed and introduced into an autoclave. Before heating the autoclave, carbon dioxid or any other indifferent gas is forced into it inorder to expel the air and produce a pres sure exceeding atmospheric, say ten atmospheres. Then the mixture is heated to the predetermined temperature for a time varying with the quantlties reacting. For 1 kilogram of pinene, the time is about 5 to 7 hours. The reactlons occurring are:-

C H +RCOOH=C H O COR C H O CO R-t-Na O H:

R COO Na+C H OH R COO Na-l-H Ac=R COO H+Na Ac.

where R is an aromatic polysubstituted acid radical, and Ac is any inorganic strong acid radical, as for instance nitric acid. After heating, the mass is discharged. The acid which has not reacted is crystallized, and the oily liquid containing the formed borneol esters in limonene solution is treated with steam, whereby the limonene is carried off and the borneol esters remain. These esters are heated for an hour with the theoretical amount, or a slight excess, of a 20% alcoholic soda solution and the alcohol is driven off. After this sa onification, the borneol is steamed off and t e remaining liquid contains the salt of the aromatic acid. The acid can be precipitated by the calculated amount of inorganic acid.

Another and more specific example of the process is as follows :385 gr. of 1.3.4 dichlorobenzoic acid, and 156 grs. of pinene are maintained throughout 6 hours at a tem-- perature of 208 in an autoclave, in which C 0 gas or any other neutral gas has been compressed through a special nozzle before the heating, in order to obtain at least 15 atmospheres pressure. This pressure is maintained through the whole time of the reaction. After cooling, the resulting mass is pressed; the oily product which is obtained, contains the limonene and the bornyl ester of 1.3.4 dichlorobenzoic acid; the limonene is driven off with steam, and the ester saponified with a little excess over the theoretical quantity of alcoholic potash solution. Then .the borneol is also driven off with steam,

the forcing in of said gas, heatin the mix:

ture to a temperature slightly higher than that at which the mixture begins to boil, so as to maintain or increase the pressure and to obtain a much higher pressure than the mass could have attainedby being heated alone in the autoclave.

2. The process of effecting the hydration of pinene to borneol and producing borneol and isoborneol esters from pinene which consists in introducing equimolecular pressure higher than that which the mixture weights of pinene and a polysubstituted orcould have attained by the heat alone in the ganic aromatic acid into an autoclave, forcautoclave.

ing an indifferent gas into the autoclave to In Witness whereof, I subscribe my signa- 5 expel the air and produce a pressure exceedture, in presence of two witnesses.

ing atmospheric, and, after the introduction I of the indifierent gas, heating the mixture GEZA AUSTERWEIL' to a temperature slightly higher than that Witnesses: at which it begins to boil, so as to maintain H. C. COKE,

10 or increase the pressure and to keep it at a MAX HERZENBERG. 

